The processing of digital audio and video, such as for transmission or for storage, has necessitated the use of various data compression technologies. A non-limiting example is the MPEG standard, that has various versions for audio as well as for video. Another standard is H.261. Realizing such compression in software has been disclosed in Ho-Chao Huang et al, New Generation of Real-Time Software-Based Video Codec: Popular Video Coder II, IEEE TR. Cons.El. Vol. 42, No. 4, P.963–973. It is feasible to have compression and similar operations executed in a mixed software and hardware environment. The number of operations necessary for software encoding is difficult to predict. An embodiment hereinafter will be mainly described with reference to video. Now, generally the compression is executed on the basis of Groups of Pictures (GOPs). Hereinafter, the term “picture” will be used consistently. Depending on the actual video standard, the term “picture” may mean “frame” as well as “field”. Now, the compression of framewise organized audio or mixed audio/video information streams may be effected in similar manner. Such processing must be done in real-time, and a high penalty must be paid in case of processor overload, by loosing pictures or parts thereof. Graceful degradation has been widely used in data processing, by surrendering a certain degree of quality in order to preserve basic system facilities.